The present invention relates generally to the manufacture of plate fin and tube heat exchangers. More particularly, the present invention relates to an apparatus used for gauging certain dimensions on the collars of plate fins to insure the proper operation of a fin press used to manufacture plate fins.
Plate fin and tube heat exchangers are widely used in a variety of applications, such as in air conditioning and refrigeration systems and in engine cooling systems. In a typical plate fin and tube heat exchanger, a fluid such as a coolant or refrigerant flows through a closed tubing arrangement while a gas such as air flows over the tubes so that heat may be transferred between the gas and the fluid. A plurality of plate fins are attached to the exterior of the tubes in the heat exchanger to increase the effective surface area of the tubes and thus enhance heat transfer
Plate fins are typically fabricated by progressively stamping a coil of plate stock and then cutting the stamped stock to a desired length to form an individual fin. The appropriate number of fins for the type of heat exchanger being manufactured are then stacked together Previously prepared U-shaped or hairpin tubes are inserted or laced through holes in tubesheets and the stacked fins and then expanded to make firm contact with the fins and tubesheets for good thermal conductivity between tube and fin as well as for structural integrity. Short U-shaped tubes, or return bends, are then attached to the ends of the hairpin tubes and secured by a suitable process such as welding, brazing or soldering to form a closed fluid flow path within the heat exchanger.
The stamping process for forming the plate fins generally comprises the use of a die to form the desired surface of the fin and to form the openings through which the hairpin tubes are laced. The openings formed have collars that project above one side of the fin and serve to separate the stacked fins one from another, thus allowing for the passage of gas through the completed heat exchanger. Because the height of the collar determines the fin spacing within the heat exchanger, that dimension is critical in assuring that the heat exchanger will function as designed. The collar diameter is also a critical dimension, for the diameter determines the quality of the joint between fin and tube when the tube is expanded. It is important for assuring the quality of the finished heat exchanger therefore that the output of the fin press be monitored and required adjustments made in order to insure that the press is producing fins having the proper collar height and diameter. In a typical manufacturing operation, it is necessary to check the collar height and diameter about once per shift.
Production or quality assurance personnel may make the height and diameter measurements using hand held scales, calipers, micrometers or the like. Such methods, however, are slow, tedious and may yield varying results depending on the skill and technique of the individual taking the measurements. There is a need, therefore, for a means of gauging the critical collar dimensions of a plate fin that is rapid, simple to operate and capable of producing accurate and repeatable results.